1. Field
Example embodiments relate to a copper electroplating solution, a copper electroplating apparatus and a method of forming a copper bump using the electroplating apparatus. More particularly, example embodiments relate to a copper electroplating solution and a copper electroplating apparatus for forming a bump on a flip chip and a method of forming the bump using the copper electroplating apparatus.
2. Description of the Related Art
Conventional semiconductor packages and board structure for a semiconductor package, for example, a printed circuit board (PCB), usually have contact terminals for electrically communicating with external bodies. For example, solder bumps and solder balls have been mainly used for the contact terminals of the packages and the board structures. Thus, the manufacturing efficiency of the packages and the board structures is influenced by the process efficiency of forming the contact terminals on the packages and the board structures.
Particularly, a chip scaled package (CSP), which has been widely used as a mini package for recent smaller-sized electronic systems, is manufactured by bonding the solder bumps to integrated circuit (IC) chips that are arranged on a semiconductor substrate, for example, a wafer. For example, the solder bump bonded to an active face of the IC chip makes contact with the contact pad of the PCB, and thus the IC chip and the PCB are manufactured into a flip chip package.
In general, the solder bump of the flip chip package is formed on the IC chip through a coating process and a reflow process. Conductive metals, for example, copper (Cu), nickel (Ni) and tin alloys (e.g., SnPb and SnAg), are coated on the electrode pads of the IC chip by an electroplating process and the coated metal layer is bonded to the electrode pad by a reflow process. Various electroplating solutions have been suggested for improving the uniformity of the solder bump by uniform metal plating and suggested for increasing the electroplating speed onto the electrode pad of the IC chip.
However, the uniformity of the solder bump and the uniform metal plating usually conflicts with the electroplating speed, and thus the uniform metal plating and the plating speed has trade-off relations. The plating speed is proportional to the intensity of the applied electrical current, and thus a larger current is required for a higher plating speed. In contrast, the current of relatively high intensity in the electroplating process usually causes locally abnormal growth of the electroplated metal and the non-uniform metal plating, which results in the non-uniformity of the solder bump. When the electrical current is applied to the IC chip at a relatively high intensity, the metal plating is likely to be performed locally under an unsteady state and thus the metal is excessively plated at some points and is insufficiently plated at other points. Therefore, the surface flatness of the solder bump is deteriorated and thus the surface area with which external bodies make contact is insufficient for the semiconductor package.
Particularly, various electroplating solutions have been suggested for copper (Cu) because copper (Cu) has been most widely used for the electroplating process for the solder bump. However, an electroplating solution of which the metal can be uniformly plated at a relatively high speed has not yet been suggested, especially for the electroplating metal of copper (Cu).